<blockquote style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;" class="gmail_quote">2011/11/25 Sam Tobin-Hochstadt <<a href="mailto:samth@ccs.neu.edu" target="_blank">samth@ccs.neu.edu</a>> This means that you passed the procedure to an untyped module with the type `Any'. If you provide a more specific type, it won't be wrapped like this. </blockquote> Indeed, I was storing a value of type FunType = (Any -> (T Any)) inside a continuation mark, and then retrieving it for the comparison. I was retrieving the continuation marks with type (Listof Any), using continuation-mark-set->list, which I think is the reason for the error I'm getting. could the continuation mark put the function in the untyped module you mention? However, if I change the expected type to (Listof FunType), I get a type error when calling continuation-mark-set->list, which says that this functions returns (Listof Any). How can I coerce a (Listof Any) into a (Listof FunType)? Or more in general, I'm facing similars problems in my code, where I get something of type Any and I need to coerce it to a more specific type but I can't get it to work. I've tried using ann and assert but it doesn't seems to work :-( Thanks for all the answers. <div class="gmail_quote"> </div> -- Ismael